If they succeed at decoupling character power from magic items and make a usable system to determine what an effective challenge for the party is based on the items they actually possess, then I don't see a mechanical need for a slot system beyond letting the DM exercise some judgement. Basically, if a person can wear something without it getting in the way of other stuff I'd say go for it. Two cloaks or two masks would still be a non-starter almost all the time, but if someone has 4 rings, and a different magical left and right boot, I have no problem with them gaining the benefit from them all. Plus we can move away from the nonsense of defining different slots for every kind of physical form. Remember Lords of Madness defining the magic item slots for a beholder? For those wondering: one headband/hat/phylactery, three goggles, three amulets/brooches/medallions/necklaces/periapts/scarabs, one belt, one pair of bracers or two bracelets, and up to three rings. Yeah, I can do without that.
That said, the flavor of many traditional D&D items come, at least in part, from where on the body it goes. I'd probably keep most of these associations (the DMG better have Boots of Haste, for example) but make it clear that these slot "restrictions" are much more about theme than mechanics. Especially compared to 3/3.5, where managing abilities that required the same slots was (IMO) tiresome more often than it was fun.
That said, the flavor of many traditional D&D items come, at least in part, from where on the body it goes. I'd probably keep most of these associations (the DMG better have Boots of Haste, for example) but make it clear that these slot "restrictions" are much more about theme than mechanics. Especially compared to 3/3.5, where managing abilities that required the same slots was (IMO) tiresome more often than it was fun.